Inductive Sensor Positioning in Rotatable Control Rods
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Solution Overview
Problem
The reproducibility of magnetic induction measurement in portable objects, such as wristwatches, is challenging due to the need for precise relative positioning of magnets and inductive sensors, which is difficult to maintain under industrial-scale production without increasing the cost.
Innovation Solution
A portable object design featuring a frame that acts as a cradle for the rotary control rod, with a magnetic ring driven by the rod and detected by an inductive sensor held against the frame's surface, ensuring precise and reproducible positioning through manufacturing precision, and using elastic means or gluing to secure the sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional magnetic sensing methods are used with indirect mounting, then device complexity is reduced, but measurement precision and reproducibility deteriorate
Solution Approach 1:
The patent merges the sensor mounting function directly into the frame structure by creating a housing integrated with the frame that holds the inductive sensor. This eliminates the need for separate mounting brackets, antimagnetic shields, and intermediate printed circuit boards, while achieving precise and reproducible sensor positioning through the frame's manufacturing tolerances alone.
2Measurement precision
If precise relative positioning of magnet and sensor is implemented, then measurement precision improves, but manufacturing cost increases
Solution Approach 1:
The patent combines the positioning function into the frame's housing structure, which is manufactured using standard injection molding processes. The housing includes integrated features such as recesses and elastic fingers that automatically position the sensor with high precision during assembly, eliminating the need for expensive specialized positioning mechanisms or manual adjustment procedures.
Solution Approach 2:
The patent utilizes the frame's manufacturing parameters (injection molding tolerances) to achieve the required positioning precision. By designing the housing features with appropriate dimensional tolerances inherent to the molding process, the system achieves reproducible sensor positioning without requiring additional precision manufacturing steps or expensive materials.
3Manufacturing precision
If multiple intermediate components are used for sensor mounting, then positioning accuracy may improve, but device complexity and cost increase
Solution Approach 1:
The patent integrates multiple functions into the frame structure: the frame serves as the cradle for the control rod, provides the housing that holds the sensor, and includes integrated positioning features (recesses and elastic fingers). This eliminates the need for separate mounting brackets, antimagnetic shields, and intermediate printed circuit boards, reducing the total component count while maintaining positioning precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design achieves reliable and reproducible detection of the control rod's rotation, maintaining high precision and consistency across multiple units, even in mass production, by determining the relative arrangement of the magnetic ring and inductive sensor solely by the frame's manufacturing precision.
Implementation Method 1
the actuation of the rotating control rod is detected by measuring magnetic induction
Implementation Method 2
the inductive sensor is held in contact with a surface of the frame by elastic means
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
portable object comprising a frame (2) arranged to serve as a cradle for a control rod (4) whose rotational actuation allows to control at least one electronic or mechanical function of the portable object, a magnetic ring (18) being driven in rotation by the control rod (4), the rotation of the magnetic ring (18) being detected by at least one inductive sensor (150) disposed in a housing (156) of the frame (2) inside of which the inductive sensor (150) is held by elastic means.